Debra Schug, Contributing Writer
For material handling facilities seeing more product flow through their operations than ever before, floor space is king. Operations not actually expanding their current footprint need to optimize every square inch, and going up can be one of the most common ways to do this.
Installing industrial racking is an important part of putting the vertical space available to work. However, racking can also play a role in better management of inventory, if the appropriate system is selected and properly installed. This article will focus on how to choose the best rack for a facility’s storage needs, as well as highlight some safety precautions which are important to avoid catastrophic rack collapses.
Racking in the Operational System
Before racking can be selected or installed, material handlers must understand that racks are just one element of a whole operational system. When considering racking, many aspects of a facility must be taken into consideration, such as the building itself, its flooring and sub-soil, as well as the handling equipment employed.
“Racks are going to perform based on a number of other factors in your facility,” Patrick Peplowski, President of the Rack Manufacturing Institute (RMI) and SpaceRAK, said during a presentation at MODEX 2018. “To name a few: slab and soil, and the strength of your racks. All that needs to work together.”
Racks themselves function as one component in a bigger setting. But, beyond that, there are many codes and standards that need to be adhered to when installing racks, including the International Building Code, RMI and American National Standards Institute. These guidelines provide details on owner responsibilities, rules on floor loading, pick-module design and safety measures to prevent product falling from racking.
Another crucial point to keep in mind is that each storage rack is designed for a specific application, in terms of its unit load and spacing of the shelving. Unit load is the total weight expected to be positioned in the rack, which includes the product load and the pallet weight. When considering the shelving space, experts advise to examine each type of pallet in a warehouse and factor in the different pallet sizes to determine the depth of the pallet racking’s frames.
Each rack should have a LARC drawing, which stands for Load Application and Rack Configuration. This document contains configuration specifics pertaining to the rack and should be kept on-hand and consulted before any new changes to the racking occur.
Additionally, don’t forget to consider the equipment that will be working in conjunction with the racking system, such as the lift trucks. Lift trucks have different lift capacities and elevated fork heights, which will determine the weight of unit load and maximum height of the pallet rack. Plus, be sure to assess how much room trucks will need to maneuver in aisles, as oversized aisles can waste precious space, while undersized aisles will render lift trucks useless in pallet racking systems.
Pallet Racking Types
There are many different types of pallet racking systems; choosing one is highly contingent on an operation’s storage needs. Each solution is designed to address a variety of issues, such as plant floor optimization, high-density storage or pallet accessibility needs.
Selective racking: This is the most common style of racking system with lower associated costs and 100% access to every pallet location; hence, the name “selective,” as anything can be selected at all times since the system is only one-pallet deep in depth. This type of system is well-suited to high SKU operations with a lot of variety in its stocking units. Less cubic utilization is a drawback, however, because one aisle must be dedicated to every two faces of a pallet on opposing sides.
Narrow aisle: This system is a type of selective racking, but has narrower aisles in order to increase warehouse capacity and minimize the need for premium aisle space. However, specialized lift trucks might be needed to navigate the smaller aisles and a possible reduction in operational efficiency could occur, because only one vehicle can move down the aisle at a time.
Double deep: This system is yet another type of selective rack, but two racks are placed back to back, and the back pallet is accessed by a specialized lift truck. This type of rack is designed to increase warehouse capacity with a higher storage density, but trucks need extensions or other specialty equipment to reach pallets and can necessitate bigger aisles.
Drive-in and drive-thru racks: These types of high-density storage racks allow lift trucks to drive in or through them. This type of racking is best suited for storage applications that have less variation in their products. However, due to accommodating truck traffic, the racking can be susceptible to more damage and selectivity of pallets can be limited. Also, another possible pitfall can be what is called “honeycombing,” which is when gaps are created in the system due to improper loading and retrieving practices.
Push-back racks: As another high-density racking solution, a push-back system can provide two to six pallets deep storage depths. A sloped rail system is designed to push pallets back using a lift truck. These systems are best for applications that can take advantage of “last in, first out” storage, most effectively with warehouses that store the same SKU in a single lane.
Pallet-flow racks: For operations that need high-density storage and deep lanes, pallet flow systems are ideal. Here, the pallet is placed in the rear of the system on a series of wheels, which utilize gravity to move the pallets forward during retrieval. These systems can be two to 30 pallets deep. However, this solution is the most expensive option, and pallets are at risk of becoming stuck.
Any operation utilizing a vertical storage system must take safety into serious consideration, because a racking disaster can cause major damage and even workplace fatalities. For proof, just search for “pallet rack collapse” to view a number of terrifying videos.
First, racks must have a uniformly distributed load (UDL), which refers to any static load that is evenly distributed over the entire surface of the rack deck. The product being stored on the deck must cover the entire deck. The capacity of a rack system is determined by the UDL stored on the deck.
However, each system will have “point loads,” which refers to any static load that is concentrated to particular points on the deck. Point loads also have a major effect on the capacity of a rack system and must be taken into consideration to determine how much weight a rack can support.
Secondly, all rack columns should be anchored, according to ANSI/RMI specifications. Anchors maintain the rack columns’ positions and resist any force put on the base of the columns, which can result from lift trucks running into them or other collisions. A properly anchored rack system entails both the aisle column and the interior or rear columns being anchored on all frames. If there is a place where the racks can’t be anchored, facilities must get permission from the manufacturer’s engineer to waive the requirement.
Thirdly, racks should be plumb and, depending on the condition of a facility’s floor, racks might need to be shimmed. Shims are plates that are placed under the rack’s base plate and ensure the storage system is level. This will help to prevent product from falling off of racks.
And finally, rack systems should be regularly inspected and maintained properly to ensure they are safe. Lift truck impact is inevitable and often goes unreported, so staff should frequently make visual checkups. WMHS